High pressure metal vapor discharge lamp with tubular current lead including filler release construction

ABSTRACT

The high pressure metal vapor discharge lamp, preferably a high pressure sodium vapor discharge lamp has an arc tube of refractory light-transmissive material such as polycrystalline alumina; it has at least one tubular lead hermetically sealed to the seals of the arc tube end portions formed with an enlarged section hermetically closed off from the exterior. The enlarged section contains the metal provided as the fill substance and a body with capillary interstices, such as a helical winding, tungsten, wool, or the like. The other end of the lead is in communication with the arc tube. The lead permits use of larger amounts of filling metal and provides dosed supply thereof to the discharge.

nite States Patent 1191 Ptaue et a1.

Johannes Pfaue; Jochen Schmidt, both of Berlin, Germany Patent-Treuhand-Gesellschaft fur Elektrische Gluhlampen mbH, Munich, Germany .Filed: Feb. 27 1973 Appl. No.: 336,368

Inventors:

Assignee:

Foreign Application Priority Data I Mar. 1, 1972 Germany 2209805 52 us. c1. 313/174, 313/178, 313/220, 313/228, 313/229 References Cited UNITED STATES PATENTS 11/1965 Schmidt 313/229 x 1m. (:1 H01j 61/22, HOlj 61/28 Field of Search 313/217, 220, 227, 228, v

3,497,756 2/1970 Knocheletal ..313 220x 3,604,972 9/1971 Levy ..313/220x 3,650,593

3/1972 Kerekes 313/220 X 5 7] ABSTRACT 1 The high pressure metal apor discharge lamp, preferably a high pressure sodium vapor discharge lamp has an arc tube of refractory light-transmissive material such' as polycrystalline alumina; it has at least one tubular lead hermetically sealed to the seals of the arc tube end portions formed with an enlarged section hermetically closed off from the exterior. The enlarged section contains the metal provided as the till substance and a body with capillary interstices, such as a helical winding, tungsten,.wool, or the like. The other end of the lead is in communication with the arc tube. The lead permits use of larger amounts of filling metal and provides dosed supply thereof to the discharge.

12 Claims, 1 Drawing Figure men PRESSURE METAL VAPOR DISCHARGE LAMP wrru- TUBULAR CURRENT LEAD INCLUDING FILLER RELEASE CONSTRUCTION CRQSS REFERENCE TO RELATED APPLICATION U.S. Ser. No. 336,371 filed Feb; 27, 1973.

' The invention relates'to a high-pressure metal vapor discharge lamp, preferably a high-pressure sodium vapor-discharge lamp comprising acylindrical discharge 'vessel or f are .tube of refractory, lighttransmissive material, preferably of polycrystalline alumina, which is hermetically sealed ateach end. It is well known to design the current supply leads of this type of lamp, at least at one end of the lmap, as an elongated tube. through which both exhaustion, as well as introduction of the'fill substance, for instance, sodiumor sodium amalgam, canbe effected (see: J apanese published patent application 45-24434; Japanesepublished 'patent application 44:8473; Br'itishPatent section of the tubular lead is closed off from the lamp interiorby a screen or a mesh. Preferably, thebody with capillary interstices comprises at least'partly metallic components which cause reduction of the temperat'ure dependence characteristic of the metal vapor by binding or fixing the sodium amalgam.

The invention will be described by way of example with reference to the accompanying drawing, wherein the single FIGURE is a vertical sectional view of' the lamp. g

Though both ends of the lamp may be sealed simultaneously, for illustration, the end A of the lamp is shown No. 1,150,262; Japanesepublished patent application 43-19716). It is also known to place sodium within the lamp, for instance, behind the filament coil (see Swiss Patent No. 498,486). Sodium may get lost during lamp operation, for example, by clean-up; In order to reduce clean-up, a suitable metal such as, for example, yttrium, cerium or the like,:can"be introduced into the lamp to react with theoxygen present therein (see French Patent No..l,562,159). Sodium amalgam may be placed in the exhaust tube. The exhaust port is covered-withagrid to supply sodium to the lamp by vaporization (see Japanese'Utility Model 44-9815).

It is an object of the invention to improve lamps of this type and provide for a-reliable supply of vaporizable metal, e.g. sodium, during the entire burninglife of the lamp.

The lamp is of the high-pressure metal vapor discharge type, preferably a high-pressure sodium-vapor discharge lamp. -It has acylindrical arc tube of refractory, light-transmissive material, preferably of polycrystalline alumina, which is hermetically sealed at each end. e

SUBJECT MATTER OF THE PRESENT ,INVENTION Briefly, the tubular'lead hermetically sealed to the seal portion of at least one end of the arc tube has'at its outer end, remote from the arc tube, an enlarged section which is hermetically closed off from the exterior. This enlarged section contains a body with capillary interstices and-the metal or metal alloy, preferably sodium amalgam,.provided as the fill substance therein; v

the interior of the tubular lead is in communication with the arc tube by way of a small aperture.

The enlarged section of the tubular lead is hermetically closed. by a lid which -is welded or soldered thereto. Its feed opening is closed by a small metal plate or disk affixed by welding or soldering.;The body with capillary interstices may be a filament coil, the turns of which abut the wall of the enlarged section of the tubu- [at lead, ora helix. The body may also be composed of a wool or randomly bunched filaments of refractory material such as, for example, tungsten wool which is filled in the enlarged section of the tubular lead; it may befo'rmed of a porous or spongy sintered body, preferably of tungsten; or of aloose mass of granules ofrefractory material. If granules are used, the enlarged means to reduce the rise of operating voltage during in a condition prior to sealing, and the end B is shown in sealed condition. v H

The are tube 1 is of polycrystalline alumina. Ring 2 is made of the same material and surrounds the hollow leads 3, 3 of niobium. The end of the lamp is additionally provided with an end cap 5 of niobium towhich the lead 3, 3 is bonded by solder 4. Interposed between front surface of ring 2 and end cap 5 is a ring 6 of glass 'solder.; The glasssolder 6 which becomes fluid during sealing, flows into the existing cavities and binds ring 2 to the arc tube 1 and to lead 3,3 as well'as to end cap 5 so that ahermetic seal of ring 2 with the other lamp parts is formed at the. end of the arc tube.

Leads 3, 3 carry respective core rods 7 and filament coils 8. Lead 3 is in communication with theinterior of the arc tube viaa small aperture 9. The lead 3 is enlarged at its outer end vto an appendix 10, which is Thehollow lead 3' is closed offv from the lamp interior by a composite disk 17, which preferably includes three stacked disks which are peripherally fused to the lead; a titanium disk of 0.2 mm thickness is embedded between two .disks' of niobium of 0.1 mm thickness. The metal support 18 welded to the end'portion of lead 3, 3 proximate the electrodeis used'to support ring 2 prior to sealing.

, The power input of the lamp is 400 W; it is filled with I xenon of 20 torr as the basic gas and with 100 mgs of sodium amalgam. The diameter of the arc tube is 7.9

mm, the electrode spacing 84 mm. The appendix 10 has a-volume of mm, 7

The location of the metal provided as for instance, sodium amalgam, in accordance with the invention affords several substantial advantages. One

of .them is that the amount of sodiumamalgam introduced may be much larger than in known lamps; mgs or more may be used without causing unstable ope'rating conditions in case of sudden overloads or in the run-in period of the lamp due to excess vaporization which may cause the lamp to extinguish. Slow release of sodium is achieved by the insertion of the body with capillary interstices which fixes the fluid amalgam by capillary forces substantially within the appendix 10.

The'possibility of introducing a larger amount of sodium without interfering with lamp operation is a fill substance,

lamp life to the extent as this rise is caused by the loss of sodium. I

Locating the amalgam in the appendix is of advantage when the rise of operating voltage is due to heat. An increase of the arc tube temperature proximate the electrodes due to a blackening of the electrode spaces and due to a variationvof the emission capacity of the electrodes results in greater increase of vapor pressure and, consequently, of operating voltage when the amalgam is located immediately behind the electrodes (i.e. internal amalgam) than when located in the appendix (i.e. external amalgam).

Increase of operating voltage in case of overload is less in lamps with an external amalgam than in lamps with an internal amalgam. When the body with capillary interstices contains metallic components which suitably bind the sodium amalgam as a function of temperature; it is possible to obtain a further flattening of the characteristic in case of thermal or electric load fluctuations.

We claim:

l. A high-pressure metal vapor discharge lamp comprising an arc tube of refractory, light-transmissive material,

hermetically sealed at each end; a tubular current lead hermetically sealed to the seal portion located'at least at one end of the arc tube;

said tubular current lead forming an enlarged section hermetically closed off from the exterior and being formed with an aperture in communication with the arc tube;

a fill substance including a metal being located in the enlarged section;

and a body with capillary interstices located in the enlarged section to retain said fill substance in the enlarged section, and to provide for dosed release of metal during operation of the lamp. 2. Lamp according to claim 1, wherein the hermetic closure of the enlarged section of the tubular lead comprises a lid which is secured thereto, and formed with a feed opening and a metal plate closing the opening and secured to the lid.

3. Lamp according to claim 1, wherein the body with capillary interstices is a filament coil which abuts with its turns the wall of the enlarged section of the tubular lead.

4. Lamp according to claim 1, wherein the body with capillary interstices is a helix.

5. Lamp according to claim 1, wherein the body with capillary interstices is a wool of refractory material, which fills in the enlarged section ofthe tubular lead.

6. Lamp according to claim 5, wherein the wool is tungsten wool.

7. Lamp according to claim 1, wherein the body with capillary interstices is composed of a porous or spongy sintered body.

8. Lamp according to claim 7, wherein the body is tungsten. v

9. Lamp according to claim 1, wherein the body with capillary interstices is a loose bulk of granules of refractory material. i

10. Lamp according to claim 1, wherein the body with capillary interstices comprises metallic components which cause reduction of the temperature dependence characteristic of the metal vapor by binding.

11. Lamp according to claim 1, wherein the lamp is a sodium vapor lamp, and the till substance including the metal in the enlarged section is sodium amalgam.

12. Lamp according to claim 11, wherein the body with capillary interstices comprises metallic components which cause reduction of the temperature dependence characteristic of the metal vapor by binding the sodium amalgam. 

1. A high-pressure metal vapor discharge lamp comprising an arc tube of refractory, light-transmissive material, hermetically sealed at each end; a tubular current lead hermetically sealed to the seal portion located at least at one end of the arc tube; said tubular current lead forming an enlarged section hermetically closed off from the exterior and being formed with an aperture in communication with the arc tube; a fill substance including a metal being located in the enlarged section; and a body with capillary interstices located in the enlarged section to retain said fill substance in the enlarged section, and to provide for dosed release of metal during operation of the lamp.
 2. Lamp according to claim 1, wherein the hermetic closure of the enlarged section of the tubular lead comprises a lid which is secured thereto, and formed with a feed opening and a metal plate closing the opening and secured to the lid.
 3. Lamp according to claim 1, wherein the body with capillary interstices is a filament coil which abuts with its turns the wall of the enlarged section of the tubular lead.
 4. Lamp according to claim 1, wherein the body with capillary interstices is a helix.
 5. Lamp according to claim 1, wherein the body with capillary interstices is a wool of refractory material, which fills in the enlarged section of the tubular lead.
 6. Lamp according to claim 5, wherein the wool is tungsten wool.
 7. Lamp according to claim 1, wherein the body with capillary interstices is composed of a porous or spongy sintered body.
 8. Lamp according to claim 7, wherein the body is tungsten.
 9. Lamp according to claim 1, wherein the body with capillary interstices is a loose bulk of granules of refractory material.
 10. Lamp according to claim 1, wherein the body with capillary interstices comprises metallic components which cause reduction of the temperature dependence characteristic of the metal vapor by binding.
 11. Lamp according to claim 1, wherein the lamp is a sodium vapor lamp, and the fill substance including the metal in the enlarged section is sodium amalgam.
 12. Lamp according to claim 11, wherein the body with capillary interstices comprises metallic components which cause reduction of the temperature dependence characteristic of the metal vapor by binding the sodium amalgam. 